Solid Polymer Electrolyte Complexes of Polyoxyethylene-Containing Star-Shaped Block Copolymers and Copolymers with Uniform Grafts

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Abstract
Ionic conductivities of salt complexes of polyoxyethylene (PEO)-containing star-shaped block copolymers and copolymers with uniform grafts were measured. The results were compared with the thermal characteristics and crystallinity of the complexes obtained from DSC and WAXD analysis. The conductivity increases with PEO content of the copolymers, more noticeably at PEO contents over 50%. For the complexes of the star-shaped block copolymers of styrene (S) and ethylene oxide (EO), conductivity decreases in the following order of salts: KCNS > NH4CNS > NaCNS. The room temperature conductivity of the KCNS complex with EO/K ratio = 20 can reach a value of 2 × 10−5 S cm−1 at 57% PEO content of the copolymer. The complex with FeCl2 displays a conductivity even higher than that of the NaCNS complex. Addition of γ-butyrolactone reduces the crystallinity and enhances markedly the ionic conductivity. For complexes of the copolymers with uniform PEO grafts the conductivity decreases in the following order of salts: KCNS > LiClO4 > FeCl2. Complexes with LiClO4 exhibit a maximum conductivity at EO/Li = 20. For different kinds of copolymers with uniform PEO grafts, conductivity of the complexes increases in the order: PS-g-PEO < PMMA-g-PEO < polymethyl acrylate-g-PEO.